Audio pitch adjustment circuit

[Chris W]

I want to take an 8 ohm, mono, audio signal that could be as high as 3
watts, and input it into a circuit that would allow adjustment of the
pitch up or down. Then it needs to output to a speaker with out
affecting the power very much. Would a circuit that could do this be
very hard to design? Or are there some out there already I can just
copy and build?

On a related note can some one tell me where I can find a simple audio
filter to filter out any frequency over 900hz and pass anything
lower.... I know I can probably find it on google but thought I would
ask while I am writing about the other circuit.

--
Chris W
KE5GIX

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[Deefoo]

I want to take an 8 ohm, mono, audio signal that could be as high as 3
watts, and input it into a circuit that would allow adjustment of the
pitch up or down. Then it needs to output to a speaker with out
affecting the power very much. Would a circuit that could do this be
very hard to design? Or are there some out there already I can just
copy and build?

On a related note can some one tell me where I can find a simple audio
filter to filter out any frequency over 900hz and pass anything
lower.... I know I can probably find it on google but thought I would
ask while I am writing about the other circuit.

--
Chris W
KE5GIX

Gift Giving Made Easy
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give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
http://thewishzone.com

Get yourself a pitch shifter (see the link for an example) and feed it into
an amp. Get yourself an equalizer for the 900Hz stuff.

http://www.harmony-central.com/Effects/Data/Boss/PS_3_Pitch_Shifter_Delay-01.html

--DF

 

[Bob Masta]

I want to take an 8 ohm, mono, audio signal that could be as high as 3
watts, and input it into a circuit that would allow adjustment of the
pitch up or down. Then it needs to output to a speaker with out
affecting the power very much. Would a circuit that could do this be
very hard to design? Or are there some out there already I can just
copy and build?

Pitch shifting is decidedly non-trivial, and doing it well is much
harder. This is one of those times when you need to carefully
examine what you are trying to accomplish and see if there is
some other way. We'd be glad to help with that if you explain
what the ultimate goal is.

If the input signal is known to be a pure sine, then you can
use an SSB approach. This is still a bit involved if the sine can
have a wide frequency range, since it typically requires a 90 degree
phase splitter. If there are harmonics in the input, this won't
give a harmonic output, however.

Audio pitch shifters are almost always done digitally. Some
very sophisticated algorithms are involved, and even still they
often have artifacts.

On a related note can some one tell me where I can find a simple audio
filter to filter out any frequency over 900hz and pass anything
lower.... I know I can probably find it on google but thought I would
ask while I am writing about the other circuit.

You need to provide more details here as well. Filters have
sloping roll-offs, so you have to decide just how steeply you
need to cut off above 900 Hz. If you can tolerate only 6 dB/octave,
then you can do this with a resistor and capacitor. Beyond that,
there are plenty of tradeoffs along with increasing complexity.

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

 

[Chris W]

Pitch shifting is decidedly non-trivial, and doing it well is much
harder. This is one of those times when you need to carefully
examine what you are trying to accomplish and see if there is
some other way. We'd be glad to help with that if you explain
what the ultimate goal is.

I have a Kenwood TS 440SA Ham radio HF transceiver. In Morse code mode
the BFO is set for a frequency of 800 hz. I would prefer a lower
frequency. If the signal is strong and you don't need any filtering
then you can simply turn on the RIT function and adjust the frequency
quite a bit either way. However if the 250hz narrow band CW filter is
being used, you are very limited in how much you can adjust the
frequency up or down. So that is what I want to do. I don't remember
the exact output of the radio to the external speaker, but I am pretty
sure it is 2 or 3 watts.

You need to provide more details here as well. Filters have
sloping roll-offs, so you have to decide just how steeply you
need to cut off above 900 Hz.

Same radio, but this time on transmit. What it actually transmits is
fine, but the in Morse code mode, instead of the 800hz tone it is
supposed to sound when you are keying, it sounds 800hz and at least 2
harmonics of 800 hz. I just don't like the way that sounds, so I want
to filter out the harmonics enough that I won't notice it. I'm not sure
if 6db per octave is enough. Last night right before MusicMatch crashed
my computer again, I had found a low pass filter circuit that claimed 24
or 36db/octave, can't remember. It was comprised of 2 op amps and
several capacitors and resistors. It didn't give a specific op amp and
I know nothing about them, so when I go to mouser.com to order one, I
will need something more specific to narrow it down from what I am sure
will be thousands of choices. It was set at 1000hz which would probably
work fine given it's high drop off rate. Now that I think about it, the
transceiver probably sends the harmonics to the transmitter too, but the
bandwidth of the TX in CW mode is probably narrow enough to reject the
harmonics.

--
Chris W
KE5GIX

Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
http://thewishzone.com

 

[Kevin Aylward]

Pitch shifting is decidedly non-trivial, and doing it well is much
harder. This is one of those times when you need to carefully
examine what you are trying to accomplish and see if there is
some other way. We'd be glad to help with that if you explain
what the ultimate goal is.

If the input signal is known to be a pure sine, then you can
use an SSB approach. This is still a bit involved if the sine can
have a wide frequency range, since it typically requires a 90 degree
phase splitter. If there are harmonics in the input, this won't
give a harmonic output, however.

Audio pitch shifters are almost always done digitally. Some
very sophisticated algorithms are involved, and even still they
often have artifacts.

Er..., well yes, they have to. An *true* up-shifter is a time machine.
You cant make things happen faster (before) they occurred.



Kevin Aylward

[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

"There are none more ignorant and useless,than they that seek answers
on their knees, with their eyes closed"